Increased throughput in the manufacture of anionic polymers by reduction in polymer cement viscosity through the addition of metal alkyls

ABSTRACT

The present invention is an improvement upon the known method of anionically polymerizing monomers by contacting the monomers with an anionic polymerization initiator which is an organo-substituted alkali metal compound. The improvement comprises decreasing the viscosity of the polymer cement by adding at least 0.01 equivalent of a metal alkyl compound per equivalent of alkali metal initiator if the metal alkyl is added before or at the beginning of polymerization. If the metal alkyl is added during the polymerization or after but before the living polymer is terminated, then at least 0.01 equivalent of the metal alkyl compound per equivalent of living polymer chain ends is should be used. The alkyl groups of the metal alkyl are chosen such that they do not exchange with the organo substituents of the alkali metal, which can be the living polymer chain ends or the organo substituents of the initiator. To avoid this undesired exchange reaction, the alkyl groups of the metal alkyl compound are selected to be more basic and/or less bulky or both than the organo substituents of the alkali metal compound.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.09/537,500, filed Mar. 29, 2000 now U.S. Pat. No. 6,391,981, whichclaims the benefit of U.S. provisional patent application Ser. No.60/130,785 filed Apr. 23, 1999.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates to the manufacture of polymers by anionicpolymerization of monomers, especially conjugated dienes and/or vinylaromatic hydrocarbons, in a hydrocarbon solvent. More particularly, thisinvention relates to an improvement in such a process whereby thethroughput of the manufacturing system is increased by reducing theviscosity of the polymer cement (the solution of the anionic polymer inthe hydrocarbon solvent).

Anionic polymers, including polymers of conjugated dienes and/or vinylaromatic hydrocarbons, have been produced by numerous methods. However,anionic polymerization of such or other monomers in the presence of ananionic polymerization initiator is the most widely used commercialprocess. The polymerization is carried out in an inert solvent such ashexane, cyclohexane, or toluene and the polymerization initiator iscommonly an organo alkali metal compound, especially alkyl lithiumcompounds. The solvent used is almost always a non-polar hydrocarbonbecause such solvents are much better solvents for the polymers of suchmonomers, especially conjugated diene polymers or blocks when they forma part of block copolymers.

As the polymer is created from the monomers, a solution of the polymerforms in the inert hydrocarbon solvent. This solution is called thepolymer cement. These polymerizations may be carried out at a variety ofsolids contents and it is reasonably obvious that if the process can berun at high solids content, the manufacturing cost will be decreasedbecause the cost of solvent will be decreased and more polymer can beproduced in a given amount of time.

Unfortunately, with polymer cements of anionic polymers, one of the mostsignificant rate limiting aspects is the viscosity of the polymercement. This is especially true in the manufacture of block copolymersof conjugated dienes such as butadiene or isoprene and vinyl aromatichydrocarbons such as styrene.

Solutions of living anionic polymers, living polymer cements, tend to behigher in viscosity than their terminated analogs, terminated polymercements. The higher viscosity of living polymer cements inpolymerization tends to limit the production capacity of equipment usedto make these products. Higher concentrations of terminated polymersolutions could be pumped and mixed with the existing equipment butpolymerization at these higher concentrations is not possible due to theprohibitively high viscosities of the living polymer solutions.Production rates are limited by the viscosity of the living anionicpolymer solutions in polymerization since the polymer chain must be kept“living”, i.e., not terminated, until the desired molecular weight isachieved.

SUMMARY OF THE INVENTION

The present invention is an improvement upon the known method ofanionically polymerizing monomers by contacting the monomers with ananionic polymerization initiator which is an organo-substituted alkalimetal compound. The improvement comprises decreasing the viscosity ofthe polymer cement by adding at least 0.01 equivalent of a metal alkylcompound per equivalent of alkali metal initiator if the metal alkyl isadded before or at the beginning of polymerization. If the metal alkylis added during the polymerization or after but before the livingpolymer is terminated, then at least 0.01 equivalent of the metal alkylcompound per equivalent of living polymer chain ends (i.e.,styryl-lithium or dienyl-lithium moiety) should be used. Preferably, inboth cases, from 0.01 to 1.5 equivalents is used and most preferably,0.01 to 1.0 equivalents.

The metal alkyl is preferably added during the polymerization but it canbe added before polymerization begins. It can also be added subsequentto polymerization before termination if desired. The alkyl groups of themetal alkyl are chosen such that they do not exchange with the organosubstituents of the alkali metal, which can be the living polymer chainends or the organo substituents of the initiator. To avoid thisundesired exchange reaction, the alkyl groups of the metal alkylcompound are selected to be more basic and/or less bulky or both thanthe organo substituents of the alkali metal compound. The organosubstituents of the alkali metal compound are aliphatic, cycloaliphatic,aromatic, or alkyl-substituted aromatic and include multi-functionalinitiators such as the sec-butyl lithium adduct of diisopropenyl. In apreferred embodiment of the invention, the organo-substituted alkalimetal species at the time of the addition of the metal alkyl is astyryl-lithium or dienyl-lithium moiety. The preferred metal alkyl foruse herein is triethyl aluminum.

DETAILED DESCRIPTION OF THE INVENTION

This invention relates to anionic polymers and processes forpolymerizing them by anionic polymerization using mono- or di- ormulti-alkali metal, generally lithium, initiators. Sodium or potassiuminitiators can also be used. For instance, polymers which can be madeaccording the present invention are those from any anionicallypolymerizable monomer, including random and block copolymers withstyrene, dienes, polyether polymers, polyester polymers, polycarbonatepolymers, polystyrene, acrylics, methacrylics, etc. Polystyrene polymershereunder can be made in the same manner as the polydiene polymers andcan be random or block copolymers with dienes.

In general, when solution anionic techniques are used, copolymers ofconjugated diolefins, optionally with vinyl aromatic hydrocarbons, areprepared by contacting the monomer or monomers to be polymerizedsimultaneously or sequentially with an anionic polymerization initiatorsuch as group IA metals, their alkyls, amides, silanolates,naphthalides, biphenyls or anthracenyl derivatives. It is preferred touse an organo alkali metal (such as lithium or sodium or potassium)compound in a suitable solvent at a temperature within the range fromabout −150° C. to about 150° C., preferably at a temperature within therange from about −70° C. to about 100° C. Particularly effective anionicpolymerization initiators are organo lithium compounds having thegeneral formula:

RLi_(n)

wherein R is an aliphatic, cycloaliphatic, aromatic or alkyl-substitutedaromatic hydrocarbon radical having from 1 to about 20 carbon atoms andn is an integer of 1 to 4. The organolithium initiators are preferredfor polymerization at higher temperatures because of their increasedstability at elevated temperatures.

Other initiators that can be used herein include multifunctionalinitiators. There are many multifunctional initiators that can be usedherein. The di-sec-butyl lithium adduct of m-diisopropenyl benzene ispreferred because of the relatively low cost of the reagents involvedand the relative ease of preparation. Diphenyl ethylene, styrene,butadiene, and isoprene will all work well to form dilithium (ordisodium) initiators by the reaction:

Still another compound which will form a diinitiator with an organoalkali metal such as lithium and will work herein is the adduct derivedfrom the reaction of 1,3-bis(1-phenylethenyl)benzene (DDPE) with twoequivalents of a lithium alkyl:

Related adducts which are also known to give effective dilithiuminitiators are derived from the 1,4-isomer of DDPE. In a similar way, itis known to make analogs of the DDPE species having alkyl substituentson the aromatic rings to enhance solubility of the lithium adducts.Related families of products which also make good dilithium initiatorsare derived from bis[4-(1-phenylethenyl)phenyl]ether,4,4′-bis(1-phenylethenyl)-1,1′-biphenyl, and 2,2′-bis[4-(1-phenylethenyl)-phenyl]propane (See L. H. Tung and G. Y. S. Lo,Macromolecules, 1994, 27, 1680-1684 (1994) and U.S. Pat. Nos. 4,172,100,4,196,154, 4,182,818, and 4,196,153 which are herein incorporated byreference). Suitable lithium alkyls for making these dilithiuminitiators include the commercially available reagents (i.e., sec-butyland n-butyl lithium) as well as anionic prepolymers of these reagents,polystyryl lithium, polybutadienyl lithium, polyisopreneyl lithium, andthe like.

The polymerization is normally carried out at a temperature of 20 to 80°C. in a hydrocarbon solvent. Suitable solvents include straight andbranched chain hydrocarbons such as pentane, hexane, octane and thelike, as well as alkyl-substituted derivatives thereof; cycloaliphatichydrocarbons such as cyclopentane, cyclohexane, cycloheptane and thelike, as well as alkyl-substituted derivatives thereof; aromatic andalkyl-substituted derivatives thereof; aromatic and alkyl-substitutedaromatic hydrocarbons such as benzene, naphthalene, toluene, xylene andthe like; hydrogenated aromatic hydrocarbons such as tetralin, decalinand the like; linear and cyclic ethers such as dimethyl ether,methylethyl ether, diethyl ether, tetrahydrofuran and the like.

It is known to polymerize such polymers with multifunctional initiatorsand then cap the living chain ends with a capping agent such asdescribed in U.S. Pat. Nos. 4,417,029, 4,518,753, and 4,753,991, whichare herein incorporated by reference. When such polymers formed withmultifunctional initiators are polymerized and then capped, a polymergel often forms. It is the subject of an earlier invention to preventthe formation of such gel by the addition of a trialkyl aluminumcompound during the polymerization/capping process. The presentinvention only relates to reduction in viscosity of living polymercement on addition of a metal alkyl and the improvement inpolymerization process throughput that results from this viscosityreduction when using initiators of the type described above under theconditions described above and does not relate to the prevention ofpolymer gels during the manufacture of capped polymers usingmultifunctional initiators.

The presence of C-Li chain ends (lithium being used herein as an exampleof an alkali metal used in the initiator) in the living polymer cementsseems to contribute to the viscosity of the solution. C-Li chain endsare the points in the molecule of the initiator where the carbon-lithiumbond is located and at which the propagation of the polymer chain occursand from which the polymer may continue to grow until it is terminated.It is known that lithium alkyls form aggregates in hydrocarbon solution.These aggregates are stabilized by metal-metal bonding between thelithium centers in the lithium alkyl moieties. Such aggregates likelyare present in living anionic polymer solutions as well. The equilibriumbetween aggregated and unassociated polymer chains appears to stronglyfavor the aggregated species. The unassociated species, though presentas a minor component of the mixture, appears to be the predominant andperhaps the only center for propagation of polymerization. For thisreason, it is important that the exchange of polymer chains betweenaggregated and unassociated centers is fast relative to the rate ofpolymerization.

The viscosity of a polymer solution is directly related to the molecularweight of the dissolved polymer. The aggregated moiety is n times largerin mass than the unassociated polymer, n representing the number ofcenters in the aggregate. For this reason, it is not surprising that theviscosity of a living anionic polymer cement (mostly aggregates) ishigher than that of its terminated analog (as a terminated chain wouldhave no C-Li centers, it is reasonable to assume that it will not beaggregated). The strong association of the C-Li chain ends in livinganionic polymer solutions is likely the source of the very highviscosity for such solutions.

We have discovered that addition of selected metal alkyls to solutionsof living anionic polymers can afford a substantial reduction in theviscosity of the living anionic polymer cement. It is preferred that themetal alkyl is selected form the group of metal alkyls that interactwith C-Li centers to form metal “ate” complexes. As an example of thistype of interaction, see the equation below in which an aluminum alkylis used as an example of the preferred type of metal alkyl and a livinganionic polymer chain end as the preferred type of aggregation pronelithium species. The “ate complex” is in equilibrium with theunassociated polymer chain. It is important that this complex is formedreversibly as the “ate complex” is not capable of either initiating orpropagating the polymerization of monomer.

It is our hypothesis that the added metal alkyl reduces the viscosity ofa living anionic polymer solution by linking the two equilibriadiscussed above. See the equation shown below.

The formation of the aluminate complex effectively drains away theaggregated polymer lithium moiety. The equilibrium concentration ofaggregated species is reduced as more of the aluminate complex isformed. As the aluminate moiety is unassociated, this mechanismeffectively reduces the concentration of aggregated species that is theprinciple contributor to viscosity in the living polymer cement. In thisway, the viscosity of the living polymer cement is minimized. As morealuminum alkyl is added, more aggregated species are eliminated, up tothe limit where all of the polymer is associated with the aluminumcenter. This appears to occur at about one aluminum alkyl per polymerlithium center. Added aluminum alkyl beyond one per polymer lithiumcenter seems to have a diminished affect on the reduction of theviscosity of the living polymer cement and at least 0.01 equivalents ofmetal alkyl per 100 alkali metal centers must be added before anyappreciable effect is noticed. Additional amounts of metal alkyl may beadded but they do not significantly further reduce the viscosity of thecement while adding additional cost and reducing the rate ofpolymerization. Therefore, it is preferred that no more than 1.5equivalents of metal alkyl be used, most preferably, no more than 1equivalent. When the metal alkyl is added during or afterpolymerization, the basis is equivalents of living polymer chain ends.When the metal alkyl is added before or at the beginning ofpolymerization, the basis is equivalents of alkali metal initiator.

The selection of the alkyl on the metal center is important for theeffective use of metal alkyls for the reduction of viscosity of a livinganionic polymer cement if additional polymerization on the livinganionic center is desired. As the formation of the metal ate complex isreversible, alkyl groups must be selected which are not prone todissociation to form RLi molecules. As outlined below using an aluminumalkyl for illustrative purposes, dissociation of the aluminate complexto form RLi and an aluminum alkyl attached to the polymer chain end iseffectively a chain transfer mechanism for the polymerization reaction.The living polymerization center, a C-Li moiety, has been transferredfrom the end of the polymer chain to the alkyl which was originally onthe aluminum species.

The polymer aluminum alkyl moiety will be inactive under typicalconditions for anionic polymerization of monomers. This polymer chain isessentially “dead” for purposes of additional polymerization reactions.If the newly formed RLi species is not an effective initiator forpolymerization of anionic monomers, the consequence of this reactionwill be to stop the consumption of monomer and terminate polymerization.If, on the other hand, the newly formed RLi species is an effectivepolymerization initiator, this reaction provides a route to generationof a new anionic polymer, one not attached to the starting polymerchain.

For typical anionic polymerization processes that are often used to makeblock copolymers having well defined structures, all of these reactionsare undesirable. Chain transfer processes like those described aboveinterfere with the orderly process normally used for making well definedblock copolymers with living polymerization systems. For such processes,it is desirable to minimize or eliminate these side reactions. It isdesirable to select alkyl groups on the metal alkyls that are being usedfor purposes of reducing the living anionic polymer cement viscositysuch that Polymer-Li species are the predominant, and desirably theonly, species which are not associated with a metal ate complex.

At equilibrium, alkyl groups that are more basic will favor beingattached to the more electronegative metal, the metal alkyl. Less basicalkyls will favor being attached to more electropositive metal, thealkali metal alkyl. The more electronegative metal is better able tostabilize the charge of a strongly basic alkyl anion. Consider theexample shown below for the distribution of alkyl groups R and R′between lithium and aluminum centers:

The selection rule for whether RLi or R′Li is the predominantunassociated lithium alkyl species present at equilibrium depends, inpart, on which alkyl is more basic. A discussion of basicity in thiscontext, and a table comparing the basicity of alkyl groups can be foundin Chapter 8 of Advance Organic Chemistry, 4^(th) Ed by Jerry March(Wiley & Sons, 1992), incorporated by reference. The basicity of alkylmoieties has been shown to follow the general trend outlined below:

In a competition for the two metal centers, it is also reasonable toexpect that more bulky alkyls will prefer to be attached to themonofunctional lithium center while less sterically encumbered alkylswill select the more highly substituted aluminum center.

In a practical application of these concepts, consider the case where aliving polymer derived from the anionic polymerization of styrene ordiene (styryl-lithium or allyl-lithium chain end) is treated withtriethylaluminum (primary alkyl group). Formation of the ate complexshould be facile but exchange of alkyls between the metal centers is notfavored. The least basic and more bulky alkyl group, styryl-lithium orallyl-lithium, will stay on lithium while the more basic and lesssterically encumbered alkyl, ethyl, will have an affinity for thealuminum center. This is a preferred system for viscosity reduction in aliving anionic polymer cement where subsequent polymerization isdesired. Aluminum alkyls having secondary or tertiary alkyls should workas well. While simple tertiary alkyl groups, such as t-butyl, can beconsidered bulky, these substituents are highly basic (as defined above)and would not be expected to participate in chain transfer reaction.Preferred embodiments include all combinations of living chains derivedfrom typical anionically—polymerizable monomers such as butadiene,isoprene and styrene and most commercially—available trialkylaluminumcompounds, including triethylaluminum, trimethylaluminum,triisobutylaluminum, tri-n-butylaluminum and tri-n-hexylaluminum.Arylaluminum compounds such as triphenylaluminum would be lesspreferred, as the phenyl ring is both less basic and fairly bulky. Theaddition of such a compound during polymerization of styrene or dienesmay result in chain transfer. These same trends would expect to beobserved for other metal alkyls that form ate complexes, such asmagnesium and zinc alkyls.

Conversely, treatment of the s-butyllithium (secondary alkyl)polymerization initiator with triethylaluminum (primary alkyl) followedby addition of monomer (thus, addition of the metal alkyl beforepolymerization) should not be an effective polymerization system. Thishypothesis was tested as outlined in a comparative example. As the ratioof triethylaluminum to sec-butyllithium was increased, the efficiency ofthe system for the initiation of the polymerization of styrene wasreduced until at 1 mole of triethylaluminum for each mole ofsec-butyllithium, the system was not able to initiate the polymerizationof styrene. For this combination of alkyls, the more basic alkyl,sec-butyl, should have an affinity for Al while the less basic primaryalkyl, ethyl, would be expected to favor the lithium center. When amolar equivalent of triethylaluminum has been added, all of thesec-butyllithium has been converted to ethyllithium which is inactive asa polymerization initiator. Since ethyllithium is an ineffectiveinitiator of styrene polymerization, the alkyl exchange reaction hasworked to remove the only effective polymerization initiator in thesystem, sec-butyllithium.

If the objective is to retain the living nature of the polymerizationand reduce the viscosity of the cement, then more care must be exercisedin the selection of the metal alkyl that is to be added to thePolymer-Li solution. In particular, the alkyl group on the “ate” complexforming metal alkyl that is to be added must be more basic and/or lessbulky than the C-Li chain end (usually styryl-Li or dienyl-Li orallyl-Li) of the living polymer. This additional requirement for theviscosity reduction agent will insure that the undesired side reactionof chain transfer will be avoided or at least minimized. In this way,viscosity reduction can be obtained without a loss in polymerizationcapability.

Alkyls of aluminum, zinc, boron (especially trialkyls such astriethylborane), and magnesium, and combinations thereof, should all beeffective for this purpose. Preferably, the alkyls have from 1 to 20carbon atoms per alkyl substituent. Preferably, the metal alkyl isselected from the group consisting of trialkyl aluminum, dialkylmagnesium, and dialkyl zinc compounds. Preferred trialkylaluminumcompounds are triethylaluminum, trimethylaluminum, tri-n-propylaluminum,tri-n-butylaluminum, triisobutylaluminum, tri-n-hexylaluminum, andtrioctylaluminum because these reagents are readily available incommercial quantities. Triethylaluminum is most preferred as it is leastexpensive on a molar basis. Preferred dialkylmagnesium compounds arebutylethylmagnesium, di-n-butylmagnesium, and di-n-hexylmagnesiumbecause these reagents are readily available in commercial quantitites.Preferred dialkylzinc compounds are dimethylzinc, diethylzinc,di-n-propylzinc, diisobutylzinc, and di-n-butylzinc because thesereagents are readily available in commercial quantities.

EXAMPLES Example 1

A general procedure was used to demonstrate how the viscosity of aliving anionic polymerization solution could be reduced significantly bythe addition of an appropriate amount of trialkylaluminum. A blockcopolymer mixture of styrene-isoprene-isoprene-styrene triblocks (SIIS)and isoprene-styrene diblocks (IS) was synthesized stepwise incyclohexane. During the experiment, viscosity data was collected atdifferent points over a number of operating conditions before and afterthe addition of trialkylaluminum. The viscosity of the living polymersolution was measured in-situ with a capillary tube apparatus. Theviscosity measurement was done by pressuring a finite amount of polymersolution through the capillary tube into a sample jar for a measuredamount of time while recording the operating pressure and temperature ofthe reactor.

An appropriate amount of polymerization grade cyclohexane was charged toa well-mixed 20-gallon stainless steel reactor vessel at 30° C. Pressurein the reactor vessel was controlled with nitrogen gas. In Step 1,styrene monomer was charged to the reactor at 30° C. The first gig ofsec-butyllithium was then added to the reactor to initiate the anionicpolymerization of the living polystyrene blocks (S). The temperature wasallowed to increase to 55° C. and the reaction was carried out for about2 hours. In Step 2a, isoprene monomer was charged to the vessel to reactwith the polystyrene blocks for about 30 minutes at 65° C. to formliving styrene-isoprene diblocks (SI). In Step 2b, a second gig ofsec-butyllithium was added to the reactor. More isoprene monomer wasthen charged to the vessel to react for about 45 minutes at 70° C. to800° C. The resulting polymer solution contained livingstyrene-isoprene-isoprene diblocks (SII) and living polyisoprene blocks(I). In Step 3, more styrene monomer was charged to the vessel to reactfor about 15 minutes at 70° C. to 80° C. The resulting polymer solutioncontained living styrene-isoprene-isoprene-styrene triblocks (SIIS) andliving isoprene-styrene diblocks (IS). The living polymer chains wereterminated by adding an appropriate amount of high-grade methanol to thereactor solution.

This experiment was carried out 3 times (Run 1, Run 2 and Run 3). Theviscosity of the living polymer solution was measured at variousoperating conditions before and after the addition of triethylaluminum(TEA) to the reactor. Each gig of TEA to the reactor had a TEA tolithium mole ratio of 0.5:1. Two TEA gigs were done in each run. Thesecond TEA gig brought the total TEA to lithium mole ratio to 1:1. InRun 1, the first gig of TEA was added to the polymer solution at the endof Step 2b. The second gig of TEA was added at the end of Step 3. In Run2, the first and second gig of TEA was added at the end of Step 3. InRun 3, the first and the second gig of TEA was added at the end of Step2b.

The materials charged for each run are given in Table 1. The reactorsolution viscosity reductions for each run are given in Tables 2, 3 and4 for Run 1, Run 2 and Run 3, respectively.

TABLE 1 Run 1 Run 2 Run 3 Step 1 Cyclohexane (kg) 40.59 40.84 32.05Styrene (kg) 0.93 0.95 1.13 sec-BuLi (g-mole) 0.089 0.089 0.106 Step 2aIsoprene (kg) 5.41 5.38 6.48 Step 2b Solids (wt %) 25.1 25.0 33.8sec-BuLi (g-mole) 0.031 0.031 0.038 Isoprene (kg) 7.28 7.30 8.79 TEA Gig(g-mole) 0.060 0.000 0.072 TEA Gig (g-mole) 0.000 0.000 0.072 Step 3Solids (wt %) 26.8 26.7 36.0 Styrene (kg) 1.24 1.23 1.60 TEA Gig(g-mole) 0.060 0.060 0.000 TEA Gig (g-mole) 0.000 0.060 0.000 Methanol(mls) 21.38 21.38 25.65

TABLE 2 Run 1 High Pressure/Shear Low Pressure/Shear S2b isoprene StepSample # 1 4 8 5 2 3 7 6 Temperature Deg C. 77.0 67.0 58.4 45.1 77.969.6 59.7 47.4 Pressure (Psig) 76.7 72.1 74.1 71.6 45.7 43.2 43.1 41.9Shear Rate (1/sec) 1891 1470 1226 1099 944.9 778.4 701.1 591.6 Viscosity(cp) 749 906 1116 1203 893 1025 1135 1308 Viscosity Change from Previous(%) 0% 0% 0% 0% 0% 0% 0% 0% S2b after TEA Gig 1 Sample # 12 13 10 16 1114 9 15 Temperature Deg C. 80.6 69.6 59.3 52.7 78.8 68.7 61.8 45.1Pressure (Psig) 74.6 75.7 74.9 74.8 43.7 43.4 45.6 43.6 Shear Rate(1/sec) 3910 3387 2420 2269 2012 1896 1481 1393 Viscosity (cp) 352 413572 609 401 423 569 578 Viscosity Change from Previous (%) −53% −54%−49% −49% −55% −59% −50% −56% S3 Styrene Step Sample # 18 19 17 20Temperature Deg C. 79.9 46.1 79.5 45.3 Pressure (Psig) 71.5 73.7 44.344.5 Shear Rate (1/sec) 3037 1906 1657 1219 Viscosity (cp) 435 714 494674 Viscosity Change from Previous (%) 23% 17% 23% 17% S3 after TEA Gig2 Sample # 24 22 23 21 Temperature Deg C. 79.9 49.8 80.1 47.2 Pressure(Psig) 72.6 74.1 42.9 43.3 Shear Rate (1/sec) 5019 2807 2730 1796Viscosity (cp) 267 487 290 445 Viscosity Change from Previous (%) −39%−32% −41% −34% S3 after Termination Sample # 27 26 28 25 Temperature DegC. 80.1 50.7 81.7 50.3 Pressure (Psig) 66.9 68.9 42.7 40.6 Shear Rate(1/sec) 6267 3190 3790 2000 Viscosity (cp) 197 399 208 375 ViscosityChange from Previous (%) −26% −18% −28% −16%

TABLE 3 Run 2 Sample # S2b Isoprene Step 1 2 3 4 Temperature Deg C 68.570.4 72.2 72.2 Pressure (Psig) 72.5 45.2 27.8 12.4 Shear Rate (1/sec)2010 1210 679.3 291.4 Viscosity (cp) 666 690 756 786 Viscosity Changefrom (%) 0% 0% 0% 0% Previous S3 Styrene Step 5 6 7 8 Temperature Deg C70.9 69.6 67.8 72.2 Pressure (Psig) 72.0 47.1 27.9 14.1 Shear Rate(1/sec) 1921 1243 709.2 367.5 Viscosity (cp) 692 700 727 709 ViscosityChange from (%) 4% 1% −4% −10% Previous S3 after TEA Gig 1 9 10 11 12Temperature Deg C 71.1 68.5 70.3 72.1 Pressure (Psig) 69.5 47.2 26.313.6 Shear Rate (1/sec) 2828 1801 1059 524.3 Viscosity (cp) 454 484 459479 Viscosity Change from (%) −34% −31% −37% −32% Previous S3 after TEAGig 2 13 14 15 16 Temperature Deg C 71.0 68.6 69.4 68.4 Pressure (Psig)70.3 45.3 26.6 12.3 Shear Rate (1/sec) 4285 2582 1523 718.1 Viscosity(cp) 303 324 322 316 Viscosity Change from (%) −33% −33% −30% −34%Previous S3 after Termination 17 18 19 20 Temperature Deg C 70.4 69.769.5 70.0 Pressure (Psig) 72.6 48.1 25.9 13.2 Shear Rate (1/sec) 38942368 1345 712.7 Viscosity (cp) 344 375 356 342 Viscosity Change from (%)14% 16% 10% 8% Previous

TABLE 4 Run 3 Sample # S2a Isoprene Step 1 2 3 4 Temperature Deg C 69.770.9 68.8 71.4 Pressure (Psig) 72.2 43.3 26.1 11.5 Shear Rate (1/sec)2847 1690 1020 462.8 Viscosity (cp) 468 473 473 459 Viscosity Change (%)0% 0% 0% 0% from Previous S2b Isoprene Step 5 6 7 8 Temperature Deg C65.5 70.9 No Cement Flow Pressure (Psig) 71.5 44.6 Shear Rate (1/sec)36.75 18.78 Viscosity (cp) 35930 43860 Viscosity Change (%) 7572% 9173%from Previous S2b after TEA 9 10 11 12 Gig 1 Temperature Deg C 71.6 71.366.7 72.7 Pressure (Psig) 73.5 44.8 23.5 9.8 Shear Rate (1/sec) 177.4105.6 40.08 12.11 Viscosity (cp) 7652 7837 10830 14940 Viscosity Change(%) −79% −82% na na from Previous S2b after TEA 13 14 15 16 Gig 2Temperature Deg C 69.1 66.7 69.2 70.0 Pressure (Psig) 73.7 47.0 26.013.7 Shear Rate (1/sec) 192.5 109 34.12 16.35 Viscosity (cp) 7069 796014070 15470 Viscosity Change (%) −8% 2% 30% 4% from Previous S3 StyreneStep 17 18 19 20 Temperature Deg C 69.4 69.6 69.6 69.6 Pressure (Psig)74.0 42.9 27.1 10.2 Shear Rate (1/sec) 247.2 127.5 77.12 20.29 Viscosity(cp) 5527 6213 6489 9282 Viscosity Change (%) −22% −22% −54% −40% fromPrevious S3 after 21 22 23 24 Termination Temperature Deg C 69.5 69.569.5 69.5 Pressure (Psig) 74.0 46.1 25.8 12.0 Shear Rate (1/sec) 265.4156 75.2 30.29 Viscosity (cp) 5149 5458 6335 7317 Viscosity Change (%)−7% −12% −2% −21% from Previous

Example 2

A series of polymers, most were block copolymers of styrene andbutadiene, were prepared under well controlled conditions. The anionicpolymerization reactions were at constant temperature with eachpolymerization step (block synthesis) targeted at a monomer chargesufficient to make a polymer segment of 5,000 molecular weight at aninitial monomer concentration of 5% wt.

Aliquots of the polymerizing mixture were collected at timed intervalsfrom the initial addition of monomer. These aliquots were quenched andassayed for solids level (by drying a known weight of sample to aconstant polymer weight). This information was used to determine thelevel of conversion of monomer to polymer as a function of time.Analysis of this information assuming pseudo-first order kinetics forthe rate of disappearance of monomer gave the rate constants shown inthe attached table.

As noted in the table, triethylaluminum (TEA) was added to some of theblock copolymerization reactions at either 50 mol % basis C-Li(Al/Li=0.5 (mol/mol)) or 100 mol % basis C-Li (Al/Li=1.0 (mol/mol)) totest the effect of added aluminum alkyl on anionic polymerizationactivity. In some instances, the aluminum alkyl was added to the s-BuLiinitiator. In others, it was added after styrene polymerization wascomplete (added to a living styryl-lithium system). In others, it wasadded after polymerization of butadiene was complete (added to a livingbutadienyl-lithium system).

In a representative example (24219-95), 0.57 gal of polymerization gradecyclohexane was charged, under an inert nitrogen atmosphere, to a 1gallon stainless steel autoclave. The Step I monomer was charged to thereactor, 100 g of polymerization grade butadiene. The solution washeated with stirring to 55° C. The initiator was added to startpolymerization, 11.92 g of 10.86% wt solution of s-BuLi in cyclohexane.The polymerization temperature was controlled at 55° C. Using the timeat which the s-BuLi was added to the reactor as the starting point,aliquots of the polymerizing solution were collected at elapsedintervals of 4, 20, 30, and 60 minutes. The samples were taken intobottles containing an excess of the quenching reagent, methanol. Theautoclave was then heated to 55° C. The living polybutadiene was treatedwith 4.41 g of a 26% wt solution of triethylaluminum (TEA) in hexane.This was sufficient TEA to react with half of the living dienyl-Li chainends. The Step II monomer was charged to the reactor, 100 g ofpolymerization grade styrene. The temperature was controlled at 55° C.Kinetic samples were collected at intervals of 4, 20, 30, and 60 minutesafter the addition of the Step II monomer. As noted above, these sampleswere collected in bottles containing an excess of methanol, thequenching reagent.

The solution containing the living polybutadiene-polystyrenyl-lithiumcopolymer (B-S-Li) with sufficient TEA to have formed an “ate” complexwith half of the living polymer chain ends was treated with the Step IIImonomer, 100 g of polymerization grade butadiene. The polymerizationtemperature was controlled at 55° C. Aliquots of the livingpolymerization solution were collected at intervals 4, 20, 30, and 60minutes following the addition of the Step III monomer. As noted above,these samples were quenched immediately to stop further polymerization.At this point, a butadiene-styrene-butadiene triblock copolymer had beenprepared. The samples collected during the three polymerization stepswere analyzed affording the data in the attached table. Variations ofthis procedure gave the data in the attached table. k is the pseudofirst order rate constant. The data show that polymerization can proceedunder the conditions of this invention.

TABLE 5 Block Experiment copolymer Monomer Ether Pzn Temp TEA TEA/LiBlock MW number sequence type (Y/N) (C.) (Y/N) (mol/mol) (GPC) k24219-77 Step I styrene N 35 N 0 5300 0.0804 Step II butadiene ″ 40-60 ″″ 8400 0.0481 24219-79 Step I styrene N 35 N 0 5259 0.1197 Step IIbutadiene ″ 48 ″ ″ 7978 0.0301 24219-81 Step I styrene N 35 Y 0.5 84990.0391 Step II butadiene ″ 50 ″ ″ 11860 0.02 24219-83 Step I styrene N35 N 0 4939 0.0949 Step II butadiene ″ 55 ″ ″ 6329 0.0782 Step IIIstyrene ″ 35 ″ ″ ˜1000 0.1152 24219-85 Step I styrene N 35 Y 0.5 82590.0568 Step II butadiene ″ 55 ″ ″ 12800 0.0744 Step III styrene ″ 35 ″ ″8100 ?? 24219-87 Step I butadiene N 55 Y 0.5 6796 0.0577 UV Step IIstyrene ″ ″ ″ ″ 10473 0.1138 UV Step III butadiene ″ ″ ″ ″ 10800 0.0825UV 24219-89 Step I butadiene N 55 N 0 6451 0.0575 Step II styrene ″ ″ ″″ 12106 0.1492 Step III butadiene ″ ″ ″ ″ 6200 0.0937 24219-91 Step Ibutadiene N 55 Y 1.0 no rxn no rxn 24219-95 Step I butadiene N 55 N 05830 0.0695 Step II styrene ″ ″ Y 0.5 14064 0.1463 Step III butadiene ″″ ″ ″ 6900 0.0797 24219-97 Step I styrene N 55 N 0 6041 0.1739 Step IIbutadiene ″ ″ Y 0.5 8039 0.0828 Step III styrene ″ ″ ″ ″ 6500 0.078524219-107 Step I styrene N 55 N 0 5201 0.1826 Step II butadiene ″ 55 Y1.0 8744 0.0582 24219-109 Step I butadiene N 55 N 0.0 4582 0.0742 StepII styrene ″ ″ Y 1.0 no rxn no rxn 24219-111 Step I styrene N 55 Y 1.07678 0.1424 24219-113 Step I butadiene N 55 Y 1.0 5804 0.026 24219-115Step I styrene N 55 Y 1.0 9864 0.0388 24219-117 Step I styrene N 55 N0.0 5111 0.4538 Step II styrene/butadiene ″ ″ ″ ″ 4766 0.0699 (40/60)24219-119 Step I styrene N 55 N 0.0 5883 0.3662 Step IIstyrene/butadiene ″ ″ Y 0.5 4666 0.0708 (50/50) 24219-121 Step I styreneN 55 N 0.0 6326 0.1389 Step II styrene/butadiene ″ ″ Y 1.0 no rxn no rxn(50/50) 24219-123 Step I styrene N 35 Y 1.0 no rxn no rxn

Example 3 Representative Procedure for Preparation of a DiinitiatedButadiene Polymer at 20% Solids in a 2 I. Glass Autoclave and Cappingwith EO after adding Trialkyaluminum

Diinitiator solutions were prepared by adding s-butyllithium to asolution of diisopropenyl benzene in cyclohexane and ether. The activeconcentration of the initiator was determined to be 0.48 N by titration.The polymerizations were carried out in a 2 liter Buchi glass autoclavewhich made any color or viscosity changes easy to observe. Unlessotherwise specified, polymerizations were carried out at a temperatureof about 35° C. to 40° C., adjusting charges for intended solids,according to the following procedure: 350 grams of cyclohexane and 100grams of diethyl ether were charged to the reactor and allowed toequilibrate to the desired temperature. 100 grams of butadiene wereadded. 203 grams of initiator solution was then added from a samplebomb, resulting in a temperature increase of about 10° C. to 20° C.After about 30 to 40 minutes, another 50 grams of butadiene was added. Athird 50 g. aliquot was added after an additional 15 to 20 minutes.After a total reaction time of about 90 to 120 minutes (estimated to beabout 8 to 10 half-lives), 57 grams of 25% wt. triethylaluminum solutionwas added, and allowed to react with the living chain ends for 15minutes. The reaction was exothermic enough to raise the temperature afew degrees. The yellow color of the polymer anion persisted, but thesolution viscosity decreased noticeably, especially at higherpolymerization solids. After 15 minutes, 6 grams of ethylene oxidecharge was added and flushed in with about 44 grams of cyclohexane froma bomb attached above it, as described in the previous example,resulting in a temperature increase of a few degrees and a decrease inthe color of the solution, but no increase in the viscosity. After 30minutes, methanol was added to terminate the reaction. Details of thisand other experiments are summarized in Table 2.

TABLE 6 Synthesis Conditions for Preparation of Diinitiated ButadienePolymers and Capping with EO After Addition of Trialkylaluminum. PolyCapping Reaction Sample # solids DiLi [DiLi] (N) RLi R₃Al TEA:Li t_(n/n)(min) EO/Li DEP 23749-75  5% 23749-33 0.48 s-BuLi None 0:1 na 1.49 Y23749-79  5% 23749-33 0.48 s-BuLi TEA 1:1 15 1.34 Y 23749-81  5% E6253S0.56 s-BuLi TEA 0.67:1 15 1.44 Y 23749-83  5% E6253S 0.56 s-BuLi TEA0.33:1 15 1.44 Y 21452-175 10% 21452-173 0.35 s-BuLi TEA 1:1 15 1.26 N21452-185 10% 21452-185 (1) s-BuLi None 0:1 na 4.4 N 21452-189 30%21452-189 (1) s-BuLi None 0:1 na 3.3 N 23749-85 10% E6253S 0.56 s-BuLiTEA 1:1 15 1.47 Y 23749-87 10% E6253S 0.56 s-BuLi TEA 0.67:1 15 1.58 Y23749-89 10% E6253S 0.56 s-BuLi TEA 0.33:1 15 1.52 Y 23749-97 30% E6269S0.52 s-BuLi TEA 1:1 15 1.6 Y 23749-101 30% E6269S 0.52 s-BuLi TEA 0.67:115 1.56 Y 23749-113 20% 23749-111 0.42 s-BuLi TEA 1:1 15 1.26 Y22930-99A 20% 167 0.49 t-BuLi TEA 1:1 15 3.08 N 22930104C 20% 7 0.57t-BuLi TEA 1:1 15 2.43 N 22930-105A 20% 7 0.57 t-BuLi TEA 1:1 15 3.21 N22930-107B 20% 9 0.5 t-BuLi TEA 1:1 15 2.41 N 22930-91A 10% 149 0.38s-BuLi TMAL¹ 1:1 15 3.01 N 22930-102A 20% 199 0.52 s-BuLi TEA 1:1 152.58 N 22930-103A 20% 191² 0.61 s-BuLi TEA 1:1 15 2.54 N 22930-109B 10%6086 0.57 s-BuLi TEA 1:1 15 1.47 N 23838-13 10% 33 0.48 s-BuLi TEA 1:115 1.38 N 23838-16 10% 33 0.48 s-BuLi TEA 1:1 15 1.58 N 23838-20 10% 330.48 s-BuLi TEA 1:1 15 1.32 N 23838-22 10% 33 0.48 s-BuLi TEA 1:1 151.52 N 23838-24 20% 33 0.48 s-BuLi TEA 1:1 15 1.37 N 23838-26 10% 330.48 s-BuLi TEA 1:1 15 1.35 N 23838-28 10% 33 0.48 s-BuLi TEA 1:1 151.47 N 23838-30 10% 6253 0.52 s-BuLi TEA 1:1 15 1.38 N 23838-32 10% 62530.52 s-BuLi TEA 1:1 15 1.24 N 23838-34 10% 6253 0.52 s-BuLi TEA 1:1 151.59 N 23838-36 10% 6253 0.52 s-BuLi TEA 1:1 15 1.17 N 23838-38 10% 62530.52 s-BuLi TEA 1:1 15 1.29 N 23838-40 10% 6253 0.52 s-BuLi TEA 1:1 151.39 N 23838-43 10% 6253 0.52 s-BuLi TEA 1:1 15 1.38 N (1) made in situin autoclave ¹Trimethylaluminum ²Triethylamine used in initiatorsynthesis instead of DEE.

Comparative Example 4 Polymerization in a 2 1. Glass Autoclave andCapping with EO after adding Diethylzinc or Dibutylmagnesium.

Butadiene was polymerized at 20% solids using an initiator prepared fromt-butyllithium and diisopropenyl benzene. After the polymerization wascomplete, one mole of diethylzinc was added per mole of lithium. As withtrialkylaluminum, the viscosity of the living polymer solutiondecreased, while the color remained essentially unchanged.

We claim:
 1. An organometallic compound prepared by the process ofcontacting anionically polymerizable monomers with a mono- ormulti-functional anionic polymerization intitiator which is anorgano-substituted alkali metal compound and adding at least 0.01equivalents of a metal alkyl compound per equivalent of living polymerchain ends, wherein the alkyl groups of the metal alkyl compound arechosen so that they will not exchange with the living polymer chainends.
 2. The organometallic compound of claim 1, wherein from 0.01 to1.5 equivalents of the metal alkyl compound per equivalent of livingpolymer chain ends is added.
 3. The organometallic compound of claim 1,wherein from 0.01 to 1.0 equivalents of the metal alkyl compound perequivalent of living polymer chain ends is added.
 4. The organometalliccompound of claim 1, wherein the metal alkyl compound is selected fromthe group consisting of aluminum, zinc, boron, and magnesium alkylshaving from 1 to 20 carbon atoms per alkyl substituent.
 5. Theorganometallic compound of claim 4, wherein the metal alkyl compound isselected from the group consisting of triethylaluminum,trimethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum,triisobutylaluminum, tri-n-hexylaluminum, trioctylaluminum,butylethyl-magnesium, di-n-butylmagnesium, di-n-hexylmagnesium,dimethylzinc, diethylzinc, di-n-propylzinc, diisobutylzinc, anddi-n-butylzinc.
 6. The organometallic compound of claim 5, wherein themetal alkyl is triethyl aluminum.
 7. The organometallic compound ofclaim 1, wherein the organo substituent of the alkali metal compound isaliphatic, cycloaliphatic, aromatic, or alkyl-substituted aromatic.
 8. Aliving anionically polymerized polymer prepared by the process ofcontacting anionically polymerizable monomers with a mono- ormulti-functional anionic polymerization intitiator which is anorgano-substituted alkali metal compound and adding at least 0.01equivalents of a metal alkyl compound per equivalent of living polymerchain ends, wherein the alkyl groups of the metal alkyl compound arechosen so that they will not exchange with the living polymer chain endsand wherein at least some of the living chain ends are an adduct of thealkali metal polymer chain end with a metal alkyl.
 9. The livinganionically polymerized polymer of claim 8, wherein from 0.01 to 1.5equivalents of the metal alkyl compound per equivalent of living polymerchain ends is added.
 10. The living anionically polymerized polymer ofclaim 8, wherein from 0.01 to 1.0 equivalents of the metal alkylcompound per equivalent of living polymer chain ends is added.
 11. Theliving anionically polymerized polymer of claim 8, wherein the metalalkyl compound is selected from the group consisting of aluminum, zinc,boron, and magnesium alkyls having from 1 to 20 carbon atoms per alkylsubstituent.
 12. The living anionically polymerized polymer of claim 8,wherein the metal alkyl compound is selected from the group consistingof triethylaluminum, trimethylaluminum, tri-n-propylaluminum,tri-n-butylaluminum, triisobutylaluminum, tri-n-hexylaluminum,trioctylaluminum, butylethyl-magnesium, di-n-butylmagnesium,di-n-hexylmagnesium, dimethylzinc, diethylzinc, di-n-propylzinc,diisobutylzinc, and di-n-butylzinc.
 13. The living anionicallypolymerized polymer of claim 12, wherein the metal alkyl is triethylaluminum.
 14. The living anionically polymerized polymer of claim 8,wherein the organo substituent of the alkali metal compound isaliphatic, cycloaliphatic, aromatic, or alkyl-substituted aromatic. 15.An organometallic compound prepared by the process of contactinganionically polymerizable monomers with a mono- or multi-functionalanionic polymerization initiator which is an organo-substituted alkalimetal compound and adding at least 0.01 equivalents of a metal alkylcompound per equivalent of living polymer chain ends wherein the alkylgroups of the metal alkyl compound are chosen so that they will notexchange with the living polymer chain ends.